diff --git a/lib/CodeGen/MachineLICM.cpp b/lib/CodeGen/MachineLICM.cpp index ffcc02e3b83..82958305445 100644 --- a/lib/CodeGen/MachineLICM.cpp +++ b/lib/CodeGen/MachineLICM.cpp @@ -34,16 +34,16 @@ namespace { class VISIBILITY_HIDDEN MachineLICM : public MachineFunctionPass { const TargetMachine *TM; const TargetInstrInfo *TII; - MachineFunction *CurMF; // Current MachineFunction + MachineFunction *CurMF; // Current MachineFunction // Various analyses that we use... - MachineLoopInfo *LI; // Current MachineLoopInfo - MachineDominatorTree *DT; // Machine dominator tree for the current Loop + MachineLoopInfo *LI; // Current MachineLoopInfo + MachineDominatorTree *DT; // Machine dominator tree for the cur loop MachineRegisterInfo *RegInfo; // Machine register information // State that is updated as we process loops - bool Changed; // True if a loop is changed. - MachineLoop *CurLoop; // The current loop we are working on. + bool Changed; // True if a loop is changed. + MachineLoop *CurLoop; // The current loop we are working on. public: static char ID; // Pass identification, replacement for typeid MachineLICM() : MachineFunctionPass((intptr_t)&ID) {} @@ -233,15 +233,14 @@ bool MachineLICM::IsLoopInvariantInst(MachineInstr &I) { return false; if (TID.mayLoad()) { - // Okay, this instruction does a load. As a refinement, allow the target - // to decide whether the loaded value is actually a constant. If so, we - // can actually use it as a load. - if (!TII->isInvariantLoad(&I)) { + // Okay, this instruction does a load. As a refinement, we allow the target + // to decide whether the loaded value is actually a constant. If so, we can + // actually use it as a load. + if (!TII->isInvariantLoad(&I)) // FIXME: we should be able to sink loads with no other side effects if // there is nothing that can change memory from here until the end of - // block. This is a trivial form of alias analysis. + // block. This is a trivial form of alias analysis. return false; - } } DEBUG({ @@ -263,12 +262,9 @@ bool MachineLICM::IsLoopInvariantInst(MachineInstr &I) { *ImpDefs; ++ImpDefs) DOUT << " -> " << TRI->getName(*ImpDefs) << "\n"; } - - //if (TII->hasUnmodelledSideEffects(&I)) - //DOUT << " * Instruction has side effects.\n"; }); - // The instruction is loop invariant if all of its operands are loop-invariant + // The instruction is loop invariant if all of its operands are. for (unsigned i = 0, e = I.getNumOperands(); i != e; ++i) { const MachineOperand &MO = I.getOperand(i); @@ -282,7 +278,8 @@ bool MachineLICM::IsLoopInvariantInst(MachineInstr &I) { if (TargetRegisterInfo::isPhysicalRegister(Reg)) return false; - assert(RegInfo->getVRegDef(Reg)&&"Machine instr not mapped for this vreg?"); + assert(RegInfo->getVRegDef(Reg) && + "Machine instr not mapped for this vreg?!"); // If the loop contains the definition of an operand, then the instruction // isn't loop invariant. @@ -294,12 +291,16 @@ bool MachineLICM::IsLoopInvariantInst(MachineInstr &I) { return true; } -/// Hoist - When an instruction is found to only use loop invariant operands -/// that is safe to hoist, this instruction is called to do the dirty work. +/// Hoist - When an instruction is found to use only loop invariant operands +/// that are safe to hoist, this instruction is called to do the dirty work. /// void MachineLICM::Hoist(MachineInstr &MI) { if (!IsLoopInvariantInst(MI)) return; + // Hoisting things that are trivially rematerializable may result in worse + // code than before. + if (TII->isTriviallyReMaterializable(&MI)) return; + std::vector Preds; // Non-back-edge predecessors.